Various adapters have been developed to add a second, outer wheel to the existing wheel of a vehicle. For example, an outer wheels may be added to each of a pair of inner wheels, positioned on opposite sides of a vehicle, to improve traction, buoyancy, stability and load bearing capability.
Smith—U.S. Pat. No. 3,068,049 discloses a transfer ring that is sandwiched between the rims of an inner and outer wheel, to create a dual-wheel vehicle. Notches in the transfer ring engage lugs welded to the surface of the rims to transfer torque from the inner wheel to the outer wheel. The transfer ring maintains the outer and inner wheels in spaced apart alignment.
Solis—U.S. Pat. Nos. 3,860,297 and 4,007,968 discloses a two part wheel accessory. A first part is mounted on the hub of the inner wheel and projects outward, and the second part is mounted on the hub of the outer wheel and projects inward. The first and second adapter parts have corresponding slots and extensions that are mateable for transferring torque from the inner wheel to the outer wheel.
Schroeder—U.S. Pat. No. 4,526,425 discloses a dual wheel mounting arrangement whereby blade-shaped spokes extending from the outer wheel mate with recesses in a hub affixed to the inner wheel. A bolt extending through the center of the second wheel engages a threaded adapter bracket in the center of the inner wheel hub, to join the two wheels together.
Brown—U.S. Pat. No. 4,818,031 discloses an outer wheel having an inwardly extending spacer sleeve with drive pins extending therefrom. The drive pins engage holes in an anchor plate attached to the outwardly facing side of the inner wheel. A bolt extending through the spacer sleeve engages a threaded opening in the anchor plate to secure the outer wheel to the inner wheel.
Meyer—US Patent Application No. 2005/0225105 discloses a convertible road and rail wheel assembly. The inner and outer wheels each have projecting shafts that are joined together by a central coupler. Torque is transferred by bolts passing through holes in the shafts and central coupler, with the holes being aligned transverse to the axis of rotation of the wheels.
Burt et al.—U.S. Pat. No. 6,848,526 disclose a vehicle with a dual wheel assembly. An inner hub connected to the inner wheel and an outer hub connected to the outer wheel are held together by a bolt extending through the center of the outer wheel and outer hub. The bolt is threaded into an opening in the inner hub. The outer hub has a pair of pins that engage slots in the inner hub to transfer torque from the inner wheel to the outer wheel.
Despite the development of prior art adapters for creating a dual-wheeled vehicle, shortcomings remain. The drive connection on many of the adapters comprises pins, clips or spokes extending from one hub that must be mated with corresponding holes, slots or recesses in the opposite hub. Often the drive connections require custom machined parts with narrow tolerances, which increases the cost of the adapters. Some of the adapters require modification of the rims of one or more of the wheels, for example, welding lugs to the rims so that a drive connection can engage the rims. Most, if not all, of the prior art adapters are customized for a particular set of vehicle wheels, wheel width and wheel spacing, and therefore lack universal application. Another drawback of the prior art adapters is that they are difficult to assemble, for example, requiring that the outer wheel be held in place while a bolt is threaded into a receiver.
These and other shortcomings in the prior art are addressed by the adapter of the present invention.